Yui and Yuki, sister-in-law of their remarried parents. Yuki is curious about Yui's body and wants to do naughty things every day aiming for a chance. Yuki secretly touches Yui's body on the bus on her way home from school, and Yui's groin sways with her first stimulating experience. Yuki who saw Yui masturbating is a lip lesbian training that hides and licks her family! Yui who was in heat also licked herself in search of Yuki's body.